A battery is a device including one or more electrochemical cells to convert chemical energy into electrical energy. Generally, an electrochemical cell of the battery includes a positive electrode and a negative electrode which are cooperated with an electrolyte producing an electrically conducting solution. When the electrodes of the cell are connected to an external circuit, the chemical energy is converted into electrical energy. However, after the manufacture of electrochemical cells, the electrodes should be activated to optimize the physical and chemical properties, such as the capabilities of self discharge and energy storage. In a cell formation process, the electrochemical cell is activated by repeat charge and discharge.